1. Field of the Invention
The present invention relates to an adsorption filter material or flat-shaped filter material which is suitable especially for the production of protective materials, such as protective suits, especially NBC protective suits, protective gloves, protective covers, as well as for other filtering applications (e.g., for air filters or medical applications). The present invention also relates to the use or application of the inventive adsorption filter material or flat-shaped filter material.
2. Description of the Related Art
There is a series of substances that are absorbed by the skin and result in severe physical damage. Examples of such substances include chemical warfare agents, such as mustard gas (yellow cross), which is a vesicant, and sarin, which is a nerve gas. Individuals who may come into contact with these toxic agents must wear a suitable protective suit or be protected against these toxic agents by suitable protective materials.
There are basically three types of protective suits: Protective suits that are impermeable to air and water vapor which are furnished with a layer of rubber that is impermeable to toxic chemical agents and cause the wearer to experience a very rapid buildup of heat; protective suits that are furnished with a membrane that allows the passage of water vapor but not the passage of the specified toxic agents; and, finally, permeable protective suits which are permeable to air and water vapor and afford the highest measure of wearing comfort.
Air-permeable materials are preferred for use in protective suits against chemical warfare agents because these suits are intended for extended use under a wide variety of conditions and must not cause heat buildup in the wearer.
Protective suits that are permeable to air generally have an adsorption layer based on activated carbon which can very stably bind or adsorb harmful or toxic chemical agents (e.g., chemical warfare agents), so that even strongly contaminated suits pose no danger whatsoever to the wearer. The adsorption layer is generally fixed on or applied to a textile substrate, especially an air-permeable substrate.
In this regard, various embodiments of the activated carbon-containing adsorption layer are known from the state of the art which generally involve a sandwich or composite construction that consists of a textile support layer, an adsorption layer joined to it, and an outer or cover layer applied over the adsorption layer.
One possibility is to use powdered activated carbon as the adsorbent which, together with a polymer binder, is printed on the textile substrate as a dispersion (see, e.g., U.S. Pat. No. 4,455,187). In this case, however, the powdered activated carbon is completely embedded in the binder and is thus completely surrounded by it. Therefore, the surface of the activated carbon is not freely accessible to the toxic substances that are to be adsorbed and the toxic substances must first migrate or diffuse through the binder to the activated carbon where they are finally adsorbed. This is not very efficient. Moreover, powdered activated carbon has only a relatively low adsorption or loading capacity for harmful and toxic substances to be adsorbed.
It is also well known that granular or spherical particles of activated carbon with mean diameters of up to about 1 mm may be used as adsorbents in protective suits of this kind instead of powdered activated carbon (see, e.g., U.S. Pat. No. 4,510,193). In this case, the adsorption layer of the activated carbon granules or spherical particles is usually formed such that the activated carbon particles are bound on spots of adhesive printed on a textile substrate. Furthermore, the adsorption layer is generally completed by an “outer material” (i.e., a cover material) and may be covered on the inner side that faces the textile substrate by a light, likewise textile material. However, although granular or spherical activated carbon particles have a relatively high total adsorption or loading capacity, the adsorption rate or adsorption kinetics is not always adequate, such that breakthroughs can occur. To avoid breakthroughs, larger amounts of activated carbon particles may be applied, but this results in over-dimensioning of the total adsorption or loading capacity that is being made available with respect to the filter material or the protective suit. Furthermore, under extreme conditions, for example, if a drop of a concentrated toxic agent falls from a considerable height onto an open place in the outer material and penetrates as far as the activated carbon, the activated carbon layer can be locally overtaxed on a short-term basis, which then also results in breakthroughs.
Finally, it is well known that activated carbon fiber woven, knitted, or nonwoven fabrics can be used as the adsorbent in air-permeable protective suits of the aforementioned type, which are bonded on one side with a textile support layer by means of a hot-melt adhesive applied over a large area and are provided with a textile cover material or “outer material” on the side facing away from the support layer (see, e.g., German patent document DE 195 19 869 C2). However, although activated carbon fibers have a relatively high initial adsorption rate or adsorption kinetics, their total adsorption or loading capacity is often inadequate, especially compared to activated carbon particles in granular or spherical form, so that in the worst case (i.e., exposure to large amounts of harmful/toxic substances), the adsorption or loading capacity of the whole protective suit may be exhausted. Moreover, under extreme conditions (e.g., if a drop of a concentrated toxic agent falls from a considerable height onto an open place in the outer material), the activated carbon fiber woven, knitted, or nonwoven fabric can be locally overtaxed on a short-term basis, so that breakthroughs may also occur. Finally, activated carbon fiber woven, knitted, or nonwoven fabrics are not always sufficiently wear-resistant under stress (e.g., during the wearing of the protective suit). Accordingly, the fibers may break and channels may form in the adsorption layer, through which the toxic substances that are to be adsorbed may then pass without hindrance.